It has long been known that a neutron detector can be made by placing a semiconductor diode adjacent to a thin film of a sensor material that reacts with neutrons. Typically, an (n,γ) or (n,α) reaction takes place in the sensor film. The interaction of the released photon or alpha particle with the semiconductor leads to the generation of electron-hole pairs that can be detected in a suitable electronic circuit.
More recently, it has been recognized that greater detector efficiency can be achieved in so-called “microstructured semiconductor neutron detectors” (MSNDs) in which the semiconductor is patterned with an array of holes or trenches filled with sensor material, or in which the semiconductor is patterned as an array of columns surrounded by a fill of sensor material.
A review and modeling study of diode detectors based on hole arrays, trench arrays, and columnar arrays is provided, for example, in D. S. McGregor et al., “Present status of microstructured semiconductor neutron detectors,” J. Crystal Growth 379 (2013) 99-110.
A recent report on columnar arrays is provided, for example, in Q. Shao, et al., “Gamma discrimination in pillar structured thermal neutron detectors,” SPIE defense security and sensing 2012” (Baltimore, Md., Apr. 23-27, 2012), published as LLNL-PROC-543492 (Lawrence Livermore National Laboratory, Mar. 30, 2012).
A patent disclosing perforated semiconductor neutron detectors diode detectors based on hole or trench arrays is U.S. Pat. No. 7,164,138, which issued on Jan. 16, 2007 to D. S. McGregor and Raymond Klann under the title, “High-efficiency neutron detectors and methods of making same.” An embodiment described in U.S. Pat. No. 7,164,138 patent utilizes a semiconductor wafer with a matrix of spaced cavities filled with one or more types of neutron reactive material such as 10B or 6LiF. The cavities may be etched via holes or etched slots or trenches.
A trench-based detector is disclosed in U.S. Pat. No. 7,855,372, issued on Dec. 21, 2010 to D. S. McGregor et al. under the title, “Non-streaming high-efficiency perforated semiconductor neutron detectors, methods of making same and measuring wand and detector modules utilizing same.” In that detector, the semiconductor is patterned as an array of sinuous fins spaced apart by a corresponding array of sinuous channels containing neutron-sensing material.
Devices such as those described in the publications and patents cited above have shown significant promise, not least because they offer advantages of ruggedness, compactness, and reliability. However, there remains a need for devices that have still greater sensitivity, as well as for devices that offer similar advantages for the detection of other forms of radiation such as gamma radiation.